Exsiccata (Latin, gen. -ae, plur. -ae) is a work with "published, uniform, numbered set[s] of preserved specimens distributed with printed labels". Typically, exsiccatae are numbered collections of dried herbarium specimens or preserved biological samples published in several duplicate sets with a common theme or title, such as Lichenes Helvetici exsiccati (see figure). Exsiccatae are regarded as scientific contributions of the editor(s) with characteristics from the library world (published booklets of scientific literature, with authors/ editors, titles, often published in serial publications like journals and magazines and in serial formats with fascicles) and features from the herbarium world (uniform and numbered collections of duplicate herbarium specimens). Exsiccatae works represent a special method of scholarly communication. The text in the printed matters/published booklets is basically a list of labels (schedae [de]) with information on each single numbered exsiccatae unit. Extensions of the concept occur.

There are several comprehensive bibliographies and treatments on exsiccatae devoted to algae, bryophytes and lichens, lichens and fungi. A printed bibliography on works devoted to vascular plants is missing. The IndExs – Index of Exsiccatae online database closes the gap.

Exsiccatae are also known under the terms exsiccatal series, exsiccata(e) series, exsiccata(e) works, exsiccatae collections, sometimes exsiccati, exsiccate. Furthermore, the feminine noun term "exsiccata" (Latin, gen. -ae, plur. -ae) for exsiccata series is often not clearly distinguished from the neuter noun "exsiccatum" (Latin, gen. -i, plur. -a) which is used in general for a dried herbarium specimen. There exists also the Latin adjective "exsiccatus, -a, -um" meaning "dried" which is sometimes used in the diagnoses of mushrooms for specimina exsiccata and is on the other hand often used in Latin titles of exsiccatae, e.g. Lichenes exsiccati.

The oldest series known as an exsiccata is that of the German naturalist and pharmacist Johann Balthasar Ehrhart [de] called Herbarium vivum recens collectum... It was distributed in 1732. The plant material and text information is for the education of physician, pharmacists and teachers. With this goal, the system of exsiccatae is originated from herbarium books with images of plants and fungi, such as the Herbaria viva distributed in the 16th and 17th century, but now contained dried and pressed plant material. Series with scholarly and scientific focus followed few years later. One of that kind of series was published by the Swiss botanist Jakob Friedrich Ehrhart, a pupil of Carl Linnaeus, with the title Plantae cryptogamae Linn., quas in locis earum natalibus collegit et exsiccavit Fridericus Ehrhart. The first fascicle was delivered in 1785. As one of the first Jakob Friedrich Ehrhart promoted the selling of dried plants with several series, among others Arbores, frutices et suffrutices Linnaei quas in usum dendrophilorum collegit et exsiccavit Fr. Ehrhart and Calamariae, Gramina et Tripetaloideae Linnaei, quas in usum botanicophilorum collegit et exsiccavit Fr. Ehrhart. Edward Hobson was an English weaver and bryophyte collector who published an exsiccata work with two bounded volumes under the title A collection of specimens of British mosses and Hepaticae, collected in the vicinity of Manchester, and systematically arranged with reference to the Muscologia Britanica, English Botany, &c, &c, &c, by Edward Hobson. [Musci Britannici] (1818–1822), a work for sale with high influence in scholarly sciences and botanists of that time.

The majority of the 2,500 known exsiccatae and exsiccata-like specimen series appeared in the 19th century. They are often specialised by a single organism group or geographical region. Two examples: Alexander Braun, Gottlob Ludwig Rabenhorst and Ernst Stizenberger have distributed Die Characeen Europa's in getrockneten Exemplaren, unter Mitwirkung mehrerer Freunde der Botanik, gesammelt und herausgegeben von Prof. A. Braun, L. Rabenhorst und E. Stizenberger in 1878 and Thomas Drummond published Musci Americani; or, specimens of the mosses collected in British North America, and chiefly among the Rocky Mountains, during the Second Land Arctic Expedition under the command of Captain Franklin, R.N. by Thomas Drummond, Assistant Naturalist ... in 1828.

Some series are devoted to organisms of economical or medicinal relevance, and thus of interest for pharmacists, plant pathologists, veterinarians, people working in horticulture, agriculture and forestry. Felix von Thümen published some exsiccatal series of this kind, e.g., Herbarium mycologicum oeconomicum.

Exsiccatae are well-known reference systems in collection-based life science and biodiversity research. Especially in early, large and widely distributed series like the Fungi Rhenani of Karl Wilhelm Gottlieb Leopold Fuckel, many taxonomic type specimens are among the 2,700 numbered specimen units, now labelled as isotypes or lectotypes.

In 2001, a web portal with underlying database called IndExs – Index of Exsiccatae was published with the goal of gathering and providing bibliographic information on all types of exsiccatae and exsiccata-like series. Currently more than 2,500 series with more than 1,300 editors are known. The editors are often well known as taxonomists. In the case that they published exsiccatae, the series are explicitly cited in Frans Stafleu and Richard Sumner Cowan's standard work Taxonomic Literature: A Selective Guide to Botanical Publications and Collections, with Dates, Commentaries, and Types (7 volumes) and in the 8 volumes of the supplement series with the first 6 co-authored by Erik Albert Mennega. How many issues (= sets) of an exsiccata is published and distributed is often unknown. In large institutional herbaria (see List of herbaria), the exsiccatae are often not kept in their original sets, but each single numbered specimen unit is inserted in the general collections and filed under the current taxon name, e.g. in M and in HUH (FH).